textproduct: Rapid City

KEY MESSAGES

- Severe storms ending early Sunday morning across south central South Dakota.

- Isolated severe storms possible Sunday night.

- Gradual warming trend through next week, with possible 100s by Friday.

UPDATE

Issued at 1036 PM MDT Sat Jun 27 2026

KUDX radar shows a line of thunderstorms ahead of a strong upper level shortwave now moving through south central SD. More storms have developed along the tail end of the line in Cherry County, NE. Short term guidance suggests, as the current line pushes into Tripp County, the NE storms will then move into western portions of south central SD. Given this, have added Tripp County to the Tornado Watch and extending the watch until 07z. Eventually these storms will move east of the CWA late tonight. Looking ahead to tomorrow...drier air behind the departing wave will hinder storm development during the daytime hours. However, surface low pressure will develop across the CO plains and move into western NE in the late afternoon and evening. A strong southeasterly LLJ will bring in very strong Theta E advection north of the low across western SD...which will support mainly elevated thunderstorms. Shear profiles in the elevated layer are mostly linear, which could support some strong/severe storms. The best chances for the overnight convection will be from the Black Hills eastward, including NW SD.

DISCUSSION

(This Afternoon Through Friday) Issued at 1017 AM MDT Sat Jun 27 2026

Current upper air models show mild ridge over the midwest region and shortwave over the MT/WY area, upper low over the PAC NW. At the surface, low pressure sits over southeastern MT, with a frontal boundary stretching down through WY. Temperatures currently sit in the upper 60s and 70s, with breezy south to southeasterly winds this morning.

Shortwave and attendant sfc low / frontal boundary slides across the region today. No shortage of available energy today, with ML CAPE values 3000-4500 j/Kg for areas east and north of the Black Hills this afternoon, while southwestern to south-central SD sit in the 1500-3000 j/Kg range. Effective shear ranges from 30-45kts as well this afternoon, making for a good supercell development day. Storms today will be capable of large hail (2"+) and strong winds (70mph+). Tornado threat is also present today, with the RAP showing northwest into central SD 50-100 helicity, LCL's around 1000-1500 meters, and sig tor of 2-3 for northwestern SD. SPC has northwestern SD in a 10% tor, which is significant for our region. CAMs show storms popping in the 19-21Z timeframe mainly over MT and WY, moving northeast. Main severe threat will be over northwestern SD for our CWA, however CAMs do try to pop a couple cells over southwestern SD mid-afternoon. Severe threat is a bit lower over the Black Hills and Rapid City area, but cannot be counted out. Storm threat runs through midnight, but by late evening, should be located closer to central SD.

By Sunday, upper low is expected over the ID/MT region, with a more southwest flow over the forecast area, and another chance for storms more in the evening to Monday morning timeframe. Isolated severe storms may be possible again, however bit less energy and shear to support widespread severe storms.

With the upper low moving east of the Rockies, temperatures dip a bit for Sunday and Monday, though still in the upper 70s and 80s. Temperatures gradually climb during the week, as main ridge builds to the east of us, and shortwave ridge builds over the Rockies. By Friday, some areas could see temps climb to around 100. WPC heat risk climbs into the moderate-major range for Thursday and Friday.

AVIATION

(For the 06Z TAFS Through 06Z Sunday Night) Issued At 1047 PM MDT Sat Jun 27 2026

VFR conditions are expected throughout the forecast period. Winds have calmed down with the exit of todays thunderstorms, and will remain docile through tonight. They will pick up Sunday afternoon with WSW gusts of 25-30mph possible.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.